For what its worth, the stupid ADCO covers are a joke. I found out first hand, the are simply a "dust cover", absolutely NOT a waterproof cover! My brand new TT developed a leak, and thank goodness I was checking for leaks even with the cover on.
If you want a cover that keeps the rain and snow from entering the camper, buy a plastic waterproof tarp from home depot, harbor freight etc. Just make sure its tied down real good. And don't believe the garbage about how the will rot the camper out because of no ventilation. I know several people who have used them for years on their campers and have never had a problem with them.